To provide an illuminating device in which variation in luminance is eliminated in the main scanning direction while suppressing power loss or component cost.

An optical fixing unit has an illuminating element array where a plurality of illuminating elements 26 arranged in matrix along the main scanning direction and the subscanning direction. The illuminating element array consists of a first block 31 having a section for correcting luminance distribution in the main scanning direction, and a second block 32 not having the luminance correcting section. The first block 31 is provided, for each row in the subscanning direction, with a current control section 36 for regulating integrated luminance of respective rows by controlling a current being supplied to the illuminating elements 26. An LED control circuit 21 checks luminance distribution in the main scanning direction and regulates illumination of the first block 31 such the luminance distribution becomes uniform. Illumination is regulated by varying the duty ratio of a control pulse signal being inputted to the current control section 36.